The present invention relates generally to a device for causing artificial respiration through an endotracheal tube or breathing mask, and particularly to such a device which permits simultaneous ventilation of a multiplicity of patients.
In certain medical procedures, it is necessary to perform direct artificial respiration by pumping air or oxygen into a patient""s lungs, which is then exhaled by the natural elastic recoil of the walls of the chest cavity, diaphragm and the lungs.
A particularly advantageous artificial breathing device, herein also referred to as a ventilator, is disclosed in U.S. Pat. No. 4,495,946 to the present inventor, the disclosure of which is incorporated herein by reference. This device may be attached by an unobstructed air duct to an outer end of a flexible endotracheal tube or breathing mask. A regulating valve is provided with its inlet side connected to an oxygen supply or other compressed gas and its outlet side connected to the unobstructed air duct through a small-bore venturi tube which extends close and generally parallel to the air duct wall in a direction towards the endotracheal tube or breathing mask. Oxygen or other compressed gas passing through the venturi into the air duct at great velocity draws air from the outside environment by injector action and presses it into the lungs of a patient. Air is then expelled by the elasticity of the lungs and the chest cavity, and can freely escape through the unobstructed air duct, which likewise permits the ejection of mucus, blood and other excretions.
The present invention seeks to provide several improvements to the ventilator disclosed in U.S. Pat. No. 4,495,946.
One object of the present invention is to provide a multiplex ventilating system capable of ventilation of a multiplicity of patients. This system is particularly advantageous for ventilating patients in a mass emergency situation such as persons whose breathing has been impaired by substances of chemical/biological warfare, for example. The system includes a central control box which is essentially a pneumatically driven, electronically controlled flow divider. The driving gas, e.g., pressurized oxygen or air, is divided by branches and directed to a plurality of ports which are fluidly connected to tubing which directs the oxygen or air to the lungs of patients.
It is known that normally, physiologically, the ratio inhalation to exhalation in a human is in the range of about 1:2 to 1:3. The present invention exploits this fact and has an operating cycle wherein at each point of the cycle, oxygen or air is pressed into the lungs of one patient, while at the same time two, or most preferably three, other patients are in exhalation. In this manner, four patients, for example, can be simultaneously ventilated at the rate of 10-15 cycles per minute. This rate is considered quite satisfactory, since for a normal person, the rate is about 12 cycles per minute. The system preferably has symmetric branches such that 8 or more persons can be simultaneously ventilated.
A particular advantage of the present invention is that at any time only one quarter of the patients are actually. drawing on the available pressure supply. This is in sharp contrast to prior art systems wherein all of the patients draw on the available pressure supply, possibly simultaneously, which is wasteful and expensive.
Another object of the present invention is to provide further improvements to U.S. Pat. No. 4,495,946, such as enhancing the driving gas (e.g., oxygen enrichment or additional moisturizing), endotracheal pressure measurement, flow measurement and ventilation by means of a transvector.
There is thus provided in accordance with a preferred embodiment of the present invention a ventilation system including a manifold fluidly connectable at an inlet thereof to a pressurized source of a driving gas, the manifold having a plurality of branches, an electronically controlled valve fluidly connected to each branch downstream of the inlet of the manifold, a ventilator fluidly connected to each of the branches downstream of the valves, each ventilator being operative to force a driving gas into lungs of a patient, and a controller in electrical communication with the valves, the controller operating the valves in accordance with an operating cycle including:
a) causing a driving gas to flow through one of the ventilators while substantially preventing flow of the driving gas through the other ventilators,
b) causing the driving gas to flow to another one of the ventilators which previously had no driving gas flowing therethrough, while substantially preventing flow of the driving gas through the other ventilators including the ventilator which previously had the driving gas flowing therethrough, and
c) sequentially repeating steps a) and b) until all the ventilators have had the driving gas flow therethrough.
In accordance with a preferred embodiment of the present invention each branch divides into two sub-branches. Preferably there are four branches.
Further in accordance with a preferred embodiment of the present invention the controller is pre-programmed or programmable to operate the valves in accordance with the operating cycle or in a high frequency mode.
Still further in accordance with a preferred embodiment of the present invention a pressure reducing valve is at the inlet of the manifold and is operative to reduce a pressure of the driving gas.
Additionally in accordance with a preferred embodiment of the present invention a regulating valve is fluidly connected to each of the ventilators for regulating flow of a driving gas through the ventilator.
In accordance with a preferred embodiment of the present invention the ventilator includes a housing with an air duct formed therethrough, a venturi tube mounted in the housing, and a second tube mounted in the housing with an opening into the air duct, the second tube being adapted for passage therethrough of a substance into the air duct. The substance may be an oxygen enrichment substance or a moisturizing additive.
Further in accordance with a preferred embodiment of the present invention the second tube is downstream of the venturi tube. Alternatively, the second tube is upstream of the venturi tube.
Still further in accordance with a preferred embodiment of the present invention the ventilator includes measurement apparatus mounted in the housing for measuring endotracheal pressure.
Additionally in accordance with a preferred embodiment of the present invention the ventilator includes a flow meter mounted in the housing for measuring flow of gas through the air duct.
In accordance with a preferred embodiment of the present invention the ventilator includes a transvector.